Glow discharge switch



Oat. 18, 1949 A. WARSHER I GLOW DISCHARGE SWITCH 2 Sheets-Sheet 1 FiledJune 6, 1944 4 INVENTOR Adolf/1 IVQIS/ZQI BY uffllwodw 1' ATTORNEYS Oct.18, 1949. A. WARSHER 2,485,520

GLOW DISCHARGE SWITCH filed June 6, 1944 2 Sheets-Sheet 2 lNVENTORAdolph, PVans/zer BY ATTO RN EY5 Patented Oct. 18, 1 949 AdolphWar-Sher, Maywoo d J., assignor to Maxwell M; Bilofsky, Newark, N; 'J.

Application-June 6, 1944;Serial No. 538,987

It is among the'objects of thei invention-to provideraglowzdischargeswitch, of simple-and rela- =tivelyinexpensive construction, which shallbe applicable in ;allrelationswhere'. it i is .desiredlautomaticallyxand sensitively toicontrol a circuit in differentiatedmanner, depending upon the magnitude on heating.- evolvedl by the glowdischarge gap, andiniwhich the operationaand; control is effectedwith'complete safety'eventh'ough the switch .b'eusedr-inenvironmentlwhere explosive gas mixtures 1 may be encountered.

The: invention :has 1 an imp'ortant application to thermioniclampsstantersaof the: glowudis'charge type and intthatl applicationfurther and more specialized? obj ectsarea-tozprovide a device of theabove type 'which shall readily. be replaceable for the conventionalglow: discharge :starter, and which shall in: addition: to itsprimaryflampsstarting function porformthe adclitional function ofpromptly and: automaticallyiinhibitingi the interr'mittent flashingofazlamp -t that 1 has .become defective, for' instance, by losstofemissive coating from its electrodes and which shalldo so :withoutzthe=:drastic curtailment: in life; incurred ".with themus'e: ofconventional glow-discharge ,lswitehes uunder: such intermittentflashing and :yet,-:.under; normal operating; conditions, with a perfectlamp, the starter shall not add: in the least to thewattage'consumed inlamp operation.

Generallyrstated; theinventioninvolves enclos-- xingrin the;hermeticallysealed envelope for the -bimetal: strip -r,usedin' theconventional bimetal v-g-lowswitch starter. for-thermionic devices, asecnd and lessrsensitive thermallyl responsive member:that,upon.sufilcient deflection thereof, effects r a circuit alternative toand distinct fromthat of the normal discharge gap-and in which circuitsufficient heat is evolved to maintain theiaddi- :tional heat responsive:element deflected until the circuit to theswitch-is opened. V

In the accompanying drawings in which are shown one" oremore of variousvpossible embodi- ,.mentsof theseveral-features of theinvention,

i Fig. 4. v

i Fig. 6' is-a--viewsimilar to Fig: I 3 of avfurther .modification, and1 2 plicationof the glow discharge switch as the starter for athermioniclamp.

Referring to :Fig. 1, the switch comprises a hermeticallysea'ledienvelope l0, desirably of glass,

.exhausted of air through tube II and charged withnoble gas'such asneon-under very low pressure.

Through the stem Id of the envelope extend the two terminals I2and 13.Upon post l5 ofthe: terminal [2 is affixed themain heatresponsive-member, desirably bi-metal'strip l6, which'carries 'a contactll, adapted to-coact-with montaot [7 upon the end of the companionelectrode ISacarried upon post l8.

aiswitching strip, desirably also of bi-metal but less sensitive andmore sluggish in-itsresponse to: heat than is the mainstrlp I6, so thatin normal o'peration, it remainssubstantially unde- Electrode I 9 isflectedpeven though-strip IE has deflected substantially. Underexcessive heat, however, the

"switch-strip I9 isdeflected in the same direction asthe main strip l6.Movable with the switching strip is a contact 20 i normally open, vbutadapted upon-sufficientdeflection of-the switching stri'p'toe'stablishcircuit to an auxiliary electrode 2| which faces the switchingstrip I9. The

;coritact:2fl-when moved by the defiected switching strip I9 closescircuit through a" connecting wire 22 from the post l5 that carries'themain strip lfi to the auxiliary electrode 2|, which is spaced fromswitching strip l9 and normally out of circuit. The glow discharge gap Gbetween the switching strip l9 and the auxiliary anode 21 -is designedto have a considerably lower voltage drop than the maindischarge gap G.This is accomplished by providing surfaces with lower workiunctions; asfor instance, by coating auxiliary anode 21 with electronemissivematerial 23am! preferably coating the corresponding face .2 4 is'carriedby theupper end of the switching stripv l9 and mounts a glass bead 25embedding the freeend-thereof. The bead has also embedded thereinbutspaced from'wire 24 .a carrying wire 26 to whichis welded a switchingmember, desirably in the formofa cross wire 22. In Fig. 1 the switchingwire 22 carries the sl 'igw'lais a circuit-diagram showing the ap- 5contact ZD -at itsinturnedleft.endZ'I. 'The right end 28 of said wire 22is downturned and has affixed rigidly thereto the auxiliary anode 2|above referred to.

Under normal operation, the heat evolved in glow discharge gap G causesdeflection of main bi-metal strip l6, to cause contacts l1 and H totouch, thereby to quench the discharge gap so that the glow dischargeswitch cools and its contacts |1|1 reopen. However, under any eventualevolution of excessive heat in gap G, the less sensitive switching stripl9 will deflect toward the right, and carry with it the switching wire23 to bring the contact 28 thereon into engagement with terminal postl5, and thereby impose upon the auxiliary anode 2| the potential ofterminal Hi, the switching strip l9 being maintained under the potentialof terminal |3. The switching strip in its deflection does not approachthe auxiliary anode 2|, since the latter is carried thereby and movestherewith, so that the distance therebetween remains constant. Since gapG has a lower work potential than gap G and the two gaps cannot bemaintained in parallel, tn;v glow discharge now is established andmaintained across gap G, and gap G is extinguished. The heat evolved ingap G is sufficient, however, to maintain the bi-metal switching stripIS in the deflected position, so that the switch remains in the settinglast described until the circuit to the glow discharge switch isinterrupted.

Since the oi-metal strips l6 and I9 flex in the same direction, the glowdischarge switch is inherently self-compensating and even a considerableincrease in the ambient temperature would not cause the contacts l1 andH to touch. It will be understood that wire 22 could be directed tocause contact 28 to engage the bi-metal strip IE or a contact thereon,instead of engaging the rod i as shown.

In the embodiment of Figs. 3, 4 and 5 are shown arrangements utilizingan electric heater in the form of an ohmic resistance, rather than anauxiliary discharge gap, to maintain the switching strip in deflectedposition after functioning thereof.

In the embodiment of Fig, 3, the post 30 and main bi-metal strip 3| areof conventional construction, as is the coacting contact 32 which,however, is mounted upon a more sluggish bimetal switching strip 33 inturn supported by the second terminal post 34. The contact 32 of saidswitching strip has in the path of deflection thereof a contact 36 onthe end of an electric heater 31 connected by wire 38 to the terminalpost 30. Desirably, contact 36 is affixed in insulating relation to wire38 which is relatively stiff. This may be accomplished by embedding thecontact end in a glass bead 39 encompassing and anchored to wire 38.Obviously, under prolonged heat, switching strip 33 is deflected towardthe right to close circuit to the ohmic resistance 3i which operates asa heater to maintain the switching strip 33 deflected and to bridge thenormal starting gap and does so until the circuit to the switch isopened.

In the embodiment of Figs. 4 and 5, the less heat sensitive bi-metalswitching strip 40 which flexes toward the left is mounted on terminalrod 4| and the main bi-metal strip 42 is mounted upon the upper end ofsaid switching strip by an intervening connector rod 43. The main strip42 flexes toward the right and coacts with a fixed anode 44 on the endof a second terminal rod 45. The latter rod is joined by connector wire46 to an electric heater 41 near the switching 4 strip 40. The lower endof the resistance 41 is connected to a terminal post 48 insulated as,for

instance, by a glass bead 49 from a wire 50, to

the upper end of which is connected the upper end of resistance 41, thelower end of wire 50 being embedded in said bead at a distance from thebead embedded upper end of wire 48.

As will be apparent, under excessive heat evolution, the deflection ofthe switching strip 40 toward the left displaces the main strip 42 awayfrom the fixed anode 44, until strip 40 engages the arm 50 of wire 50.Circuit is now established from terminal 4| through switching strip 40,wire 50 and resistance 41 to the opposite terminal 48. The heat evolvedby the resistor 41 maintains the switching strip 40 deflected andbridges the gap between strip 42 and anode 44 until the main switch isopened.

In the embodiment of Fig. 6, the terminal post 60 carries the mainbi-metal strip 6| of U-form, facing in one direction and the bi-metalswitching strip 82 also of U-form but of more sluggish action facing inthe opposite direction. The contact 63 of the main bi-metal strip 6|coacts with the anode 64 on the second terminal post 65. The electricheater resistance 61 is near but spaced from switching strip 82 and inthe path of movement of the free end thereof.

The lower end of heater 81 is affixed to post 55, the upper end of whichis embedded in glass bead 56 in which is embedded the lower end of wire51 that mounts the upper end of heater 61. Conductor 86 externally ofthe envelope connects post 65 to post 55. Thus, in operation, when theswitching strip is deflected under prolonged heat, it closes circuit tothe resistance 61 by engagement of contact 68 on the switching stripwith contact 69 upon the upper heater mounting wire 51. The heat evolvedin heater 61 is sufficient to keep the switching strip 62 deflecteduntil the main circuit is opened. With the resistance thus in circuitthe glow discharge gap between strip BI and anode 84 is bridged byheater 81.

The entire glow discharge switch in each of its embodiments ishermetically sealed in its envelope l0 so that it may be used safely,even in an atmosphere in which explosive mixtures are sometimes present.

In Fig. '1 is shown the circuit diagram of an important application ofthe glow discharge switch in one of its various uses, i. e., for thestarting of a conventional thermionic lamp L with electrode filaments atthe opposite ends thereof, each coated with an emissive coating ofbarium oxide or strontium oxide according to conventional practice.

The glow switch starter S of any of the embodiments shown is in thestarting circuit 18, which connects lamp electrodes 1| and 12 in series,for electrically heating the same. An iron core ballast coil 13 is inthe line and the lowering of the power factor of the system due to itsoperation is compensated for by condenser 14 across the line, all inaccordance with conventional practice.

In the operation of the conventional glow switch starter, the appliedvoltage is at the outset suflicient to cause the glow discharge in gapG, but is insufficient to cause arcing of the lamp L. If starter S is ofthe construction shown in Figs. 1 and 2, the bimetal strip I6 thereofunder the heat of the glow discharge, deflects to close circuit tocontact |1' while storing energy in ballast coil 13. The glow dischargeis thus interrupted with resultant cooling and contraction of the=bimetal strip- H away from contact I'll. As :xa'result-of this openingofthe starter: circuit, the

impulse-fromthe-ballastcoil 13 tends torstart therarc inthe lamp Lacrossits now= heated electrodes'l l and Hand the starting cycle set forthis'rres-umed until the arc. in the lamp: L has actually been str-uck andsincesuch arc when once maintained requires voltage less than that.required to initiatethe glow discharge in the "starter -SWibICh S thelatter remains outof action.

Should thelampbeco-me defective, as for instance, due-to the loss ofemissive material from oneor both of its electrodes, so that the lampwill 'falterinsted: ofmaintaining its arc, the conventional glow switchstarter (devoid of the present improvement), would repeat the cycleabove set forth andcause the lamp intermittently to flash 1 onan'd ofhtothe annoyance of the user and with very-short life of the glow-dischargeswitch.

With: the glow switch of the presentinvention,

however (illustratively of the embodiment of Figs. 1 and 2), should theglow discharge in gap G bermaintained' for an abnormal length of time,duetotthe slowness in starting or restarting of a defective lamp, theless sensitive bi-metal strip 1 Ma -which in normal operation will notmove, is

caused to flex, to bring the switching wire' 22 into engagementwiththepost l5 and to apply the potential of said post upon the auxiliary anode2|. By reason of the lower work function of the electrodes of glowdischarge gap G, the glow discharge is promptly set up betweenzswitchingplate I!) and auxiliary anode 2|. The glow discharge in gap G evolvessufficient heat to maintain the bimetalzstrip I9 deflected andlthat glowdischarge isthus maintained as long as the main switch 'lfizcontrollingthe lamp L is-cclosed.

.Byyreason of its electrodes of lower work function, the existence ofthe glow discharge across gap G precludes the possibility of the glowdischarge resuming across the-main discharge gap G. The intermittentflashing of a defective lamp L is therefore precluded as is therepetition of the cycle of operations of the bi-metal strip I6.Accordingly, the glow discharge switch of the present invention is notsubject to rapid wear and will serve for many thousands of hours use.

From the foregoing description, the mode of operation of the glowdischarge switches of the embodiments of Figs. 3 to 6, when used asthermionic lamp starters, will be clear without the need for furtherdescription.

In each embodiment, it is seen that the use of the present improvement,does not involve the slightest alteration in the mode of operation ascompared with the operation of a conventional glow starter switch upon aperfect lamp. The presence of the added safety switching feature doesnot add in the least to the power consumption as long as the glowstarter switch of the present invention is used with a good lamp.

The glow discharge switch in each of its embodiments is, of course,useful as an automatic control switch in a wide variety of applications,in fact, in any relation in which the evolution of heat in the switch,upon exceeding a predetermined minimum is automatically to effect someswitching in the circuit connections.

The glow switch starter is a unit of small bulk, in fact in its lampstarter form, it is of bulk so small that there is no need foralteration in the thermionic lamp fixtures now in use that are designedfor conventional glow switch starters, to enable replacement of thelatter by the im- 6 proved glow switch starter of;- the: presentinvention.

By the term glow 'discharge.- switch as used in'the claims: ismeant aunit. of the-general; character described, which is charged with anoblegas or mixture: of. noble gases; at pressure; such as to develop. a glowdischarge across itselectrodes at voltageacontrolling'a step inthe operationof thesystemordevice with. which it.is used.

As many changescould be-made1 in the above construction and: manyapparently widely different embodiments of this invention could be madewithout departing: from the scope-of. the claims, it is. intended thatall matter contained in'thea'bove description or showninitheiaccompanying: drawings shall be interpreted aszillustrative andnot in a. limiting sense.

Having thus described my invention, what. I claim as new andrdesire tosecureby Letters-Patent' of. the United. States is:

1. A glow discharge switch comprising; an: envelopehaving apair ofbi-metalrelectrodes spaced for glow discharge therebetween,one'ofsaidxelectrodes being less sensitive'toheat than; the other andflexing away from the latter to serveas; a switching electrode under theprolonged. evolution. of heat in the glowzdischargeegap; am auxiliaryelectrode spaced from/said. switching electrode'andiout of circuit under.normal operation, and means under controlof said: switching electrodeand carried. thereby to close thecircuitto said auxiliary electrodethereby to efiectaglow discharge between the switching and. theauxiliary electrode, said latter glow discharge circuit havingsuflicient heat evolution tomaintain. the switching electrode in itsdeflected positionwas longas the circuit remains closed.

2. A glow discharge switch, comprising anenvelope having therein a pairof bi-metal strips spaced for a main. glow dischargetherebetween,terminals carrying the same, one of said strips being of less heatsensitivity than the other, being arranged to deflect away underprolonged heating and constituting a switching strip, an auxiliaryelectrode movable with and spaced from said switching strip foralternative glow discharge therebetween and having electrodes of lowerwork function than those of said main glow discharge, and meansresponding to the movement of said latter strip for electricallyconnecting the auxiliary electrode with the terminal of the otherelectrode to initiate the alternative glow discharge, the switchingstrip being exposed to the heat generated by said alternative glowdischarge and maintaining the latter until the circuit to the glowdischarge switch is opened.

3. A glow discharge switch comprising an envelope having fixed terminalsextending thereinto, bi-metal strips afiixed to said terminalsdetermining a discharge gap therebetween, and having coacting contactportions normally spaced from each other, one of said bi-metal stripsbeing less sensitive to heat than the other and serving as a switchingstrip upon deflection thereof under prolonged heating, an auxiliaryelectrode movable with and insulated from said switching strip, saidauxiliary electrode and said switching strip being spaced from eachother and defining an alternative glow discharge gap therebetween, aconnector under control of said switching strip for establishingelectrical contact from said auxiliary electrode to the terminal of theother strip, said switching strip being exposed to the heat evolved inthe alternative glow discharge gap,

thereby to maintain said switching strip de- 4. A glow discharge switchcomprising a hermetically sealed envelope, a pair of electrode postsextending thereinto, a main bi-metal stri rigid at its root with one ofsaid posts, a switching bimetal strip rigid at its root with the otherof said posts, said strips being spaced for a main glow discharge gaptherebetween, a switching member carried by said switching strip andinsulated with respect thereto, an auxiliary electrode carried by saidswitching member near one end thereof facing but spaced from saidswitching strip for alternative glow discharge gap having elements ofwork function lower than those of said main glow discharge gap, saidswitching member being normally spaced at its opposite end from theelectrode post of the main bi-metal strip and closin circuit thereto bythe movement of the switching strip under prolonged heat, the heatevolved in the alternative glow discharge gap being sufficient tomaintain the switching stri deflected until circuit is opened.

5. A glow discharge switch comprising a hermetically sealed envelopehaving a pair of bimetal electrodes therein spaced for glow dischargetherebetween of higher work function, terminals therefor, saidelectrodes including a main bi-metal strip, a bi-metal switching stripless sensitive to heat than said main strip so as to deflect materiallyonly under prolonged heat, a switching member carried by said switchingstrip and insulated therefrom, an auxiliary electrode carried by one endof said switching member, said auxiliary electrode and said switchingstrip being spaced to define an alternative glow discharge gaptherebetween, the other end of said switching member being adjacent themain bi-metal strip and serving to switch said auxiliary electrode intocircuit by deflection of the switching strip away from the main stripunder applied heat, the heat evolved in the alternative glow dischargegap being sufiicient to keep the switching strip deflected until thecircuit is interrupted.

6. The combination recited in claim 5 in which a glass bead wire mountedupon the switching strip mounts the switching member in electricallyinsulating relation with respect thereto.

7. A glow discharge switch comprising a hermetically sealed envelopehaving terminal posts therein, a bi-metal main strip on one of saidposts, a coacting bi-metal switching strip on the other of said posts,and of lesser rate of deflection than said main strip and a switchingwire carried by said switching strip and insulated therefrom, said wirehaving a downturned end portion, an auxiliary electrode afiixed thereto,facing said switching strip and having an emissive coating thereon, theother end of said wire being movable under the deflection of saidswitching strip to apply potential from the post carrying the main stripto the auxiliary electrode, the discharge gap to said auxiliaryelectrode having elements of lower work function than that across thebi-metal strips, the heat evolved in the discharge gap to said auxiliaryelectrode being suflicient to maintain the switching strip deflecteduntil the circuit is opened.

ADOLPH WARSHER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,274,399 Cook Feb. 24, 19422,355,476 Smith Aug. 8, 1944 2,367,655 Atkins Jan. 23, 1945 2,372,149Townsend Mar. 20, 1945 2,408,493 Townsend Oct. 1, 1946 2,427,741 PetersSept. 23, 1947

